The method of analyzing the genetic structure has been remarkably progressed in recent years. A large number of genetic structures represented by those of human genes have been clarified. The analysis of the genetic structure uses a DNA microarray (DNA chip) in which several thousand to not less than ten thousands kinds of different types of DNA fragments are aligned and fixed as spots on a base plate such as a microscopic glass slide.
In recent years, there is a demand for enhancing the reproducibility, the quantitative performance in the information obtained from the DNA microarray and obtaining much more information from the DNA microarray. The information obtained from respective spots needs to be correct, uniform, and complex.
Those widely used as the method of forming the spots for the production of the DNA microarray are generally based on a system such as the QUILL system, the pin & ring system, and the spring pin system in which a sample solution containing DNA fragments is supplied (stamped) onto the base plate by using a so-called pin. When any one of the foregoing methods is adopted, it is important to suppress the dispersion of the volume and the shape of each spot so that the distance between the respective spots is maintained to be constant.
On the other hand, in order to realize a higher density, it is also greatly expected to develop a new method which is excellent in productivity and in which the shape control performance for the spot is satisfactory.
The conventional method of forming the spot is based on the supply (stamping) of the sample solution onto the base plate by using the pin. Therefore, the shape of the spot is diversified, for example, due to the shape of the forward end of the pin and/or the residue of the sample solution remaining at the forward end of the pin after the supply. As shown in FIG. 18, spots 200, each of which has many irregularities at the outer circumferential portion, are formed on a base plate 202.
When unknown DNA is inspected by using a DNA microarray arranged with a large number of spots having dispersed shapes, it is apt to be difficult to recognize the fluorescence light emission from the spot with a CCD camera or the like. Therefore, the inspection accuracy may be lowered.
Further, when many irregularities exist at the outer circumferential portion, the sample solution flows through angular portions. Therefore, the sample solutions in the plurality of spots 200 may be mixed with each other.
The present invention has been made taking the foregoing problems into consideration, an object of which is to provide a DNA microarray which makes it possible to improve the inspection accuracy for genetic analyses and which makes it possible to increase the amount of information to be obtained.
Another object of the present invention is to provide a DNA microarray which makes it possible to achieve a high degree of concentration of spots and which makes it possible to perform detailed genetic analyses.
Still another object of the present invention is to provide a DNA microarray which makes it possible to recognize the degree of the reaction with respect to an amount of DNA fragments immobilized in a spot and which makes it possible to obtain an analog inspection result for a specimen, in addition to a digital inspection result to indicate whether or not the reaction occurs.
The applicable range of the present invention is not limited to the DNA microarray in which DNA fragments are aligned and immobilized as spots. The present invention is generally usable for every type of the biochip which specifically reacts with a biochemical specimen and which is used in order to obtain information on the structure of the specimen.